This invention relates to a process for making a granular detergent product and the product of the process. More particularly, the invention relates to a process for preparing detergent compositions which are useful in automatic dishwashing machines.
Detergent compositions comprising in combination an alkali metal polyphosphate such as sodium tripolyphosphate, alkaline salts such as sodium silicate and optionally sodium carbonate, and optionally a chlorine containing compound that provides hypochlorite ion in solution have particular utility for machine dishwashing. The production of such compositions made of agglomerates of the ingredients has been generally accomplished by the addition of an aqueous sodium silicate solution to a mixture of dry ingredients. However, compositions prepared in such manner are characterized by a tendency to cake in their cartons during storage and can also have a tendency to cake in the dispenser cups of automatic dishwashing machines. A number of process modifications have been suggested to reduce the caking tendency of detergent compositions prepared using silicate solutions as agglomerating agents. U.S. Pat. No. 2,895,916 discloses an order of addition in which a chlorine containing compound, chlorinated trisodium phosphate, is added to the composition only after the aqueous silicate has been added to an anhydrous polyphosphate. The benefit is said to result from a more rapid hydration of the sodium tripolyphosphate in the absence of chlorinated trisodium phosphate.
It has now been found that a substantial reduction in the carton caking tendency of agglomerated detergent compositions containing alkali metal polyphosphates and alkali metal silicates can be achieved if from about 2% to about 20% of a hydratable salt other than alkali metal silicate is incorporated in the aqueous silicate solution used to agglomerate the alkali metal polyphosphate and optionally other dry ingredients.
Accordingly, it is an object of this invention to produce agglomerated granular detergent compositions which are resistant to carton caking.
Other objects and advantages will be apparent from the following description and examples.